I have imported my polylines into GRASS using v.in.ogr and converted them to 3D using v.to.3d. I checked the lines using the GRASS info tool and the polylines all have the correct z values. I then exported it using v.out.dxf but this is where I am having troubles.

The dxf contains the z values for the polylines:

Extract

VERTEX
8
line
10
401120.708496
20
6875185.007069
30
539.000000
0

However when I open it in AutoCAD Civil 3D it doesn't recognize the z value and just makes all the lines 2D. I have checked them with the info tool in AutoCAD but the z values are all the same.

Is the dxf created using v.out.dxf supported in AutoCAD in order to get correct 3D?

I guess my goal is to be able to send a 3D dxf from our GIS software to consultants. We only have one copy of Civil 3D and that is used by the design guy pretty much full time.
–
Nathan WFeb 9 '11 at 23:17

and you want to use grass to create. or esri? Sorry but the process is so easy from civil3d I think I would script it and use the design machine at night. or use export to cad from esri.
–
Brad NesomFeb 10 '11 at 2:36